This invention relates to a catalytic process for the preparation of tetrahydrofuran and gamma-butyrolactone from at least one of maleic anhydride or succinic anhydride. More specifically, this invention relates the use of a catalyst comprising the mixed oxides of copper, zinc and aluminum wherein the catalyst is coated in a thin layer onto an inert support material.
Tetrahydrofuran is a useful solvent for natural and synthetic resins and is a valuable intermediate in the manufacture of a number of chemicals and plastics. Gamma-butyrolactone is an intermediate for the synthesis of butyric acid compounds, polyvinylpyrrolidone and methionine. Gamma-butyrolactone is a useful solvent for acrylate and styrene polymers and also a useful ingredient of paint removers and textile assistants.
It is known in the art that tetrahydrofuran and gamma-butyrolactone may be produced by a number of different methods. For example, tetrahydrofuran can be produced by the dehydration of 1,4-butanediol and gamma-butyrolactone can be prepared by the dehydrogenation of 1,4-butanediol. Specifically, most tetrahydrofuran and gamma-butyrolactone are manufactured in a multi-step sequence starting with the reaction of acetylene and formaldehyde in the presence of a cuprous acetylide complex to form butynediol. The butynediol is reduced to butanediol, which is dehydrated to tetrahydrofuran and dehydrogenated to gamma-butyrolactone as indicated above.
In addition, tetrahydrofuran and gamma-butyrolactone can be prepared by catalytic hydrogenation of maleic acid, fumaric acid and succinic acid, their respective anhydrides and ester derivatives.
The instant invention focuses on the production of tetrahydrofuran and tetrahydrofuran with gamma-butyrolactone from maleic anhydride and/or succinic anhydride. Specifically, the instant invention focuses on a fixed bed vapor phase process for the hydrogenation of maleic anhydride to tetrahydrofuran and gamma-butyrolactone in the presence of a hydrogenation catalyst.
The catalysts used in most fixed bed reactors typically are a powder which has been compressed into pellets or a slurry which has been extruded into a cylinder or other shapes and then dried. Typically, such pellets and extrudates are 1/8 inch or larger for use in commercial fixed bed reactors. It has now been discovered that such large pellets favor the production of tetrahydrofuran. An object of this invention is a fixed bed catalyst which would favor gamma-butyrolactone production.
In part, the instant invention relates to supported catalysts. The use of supports for catalysts is well known in the art. In a traditional sense, the support is normally considered to be a very small particle that provides a base for the active catalytic material. This supported catalyst is then agglomerated to provide a tablet having an essentially uniform catalyst composition throughout. The present invention is different from this art in that the catalytic material is coated onto a massive support, and a nonhomogeneous catalyst composition is obtained.
A method for coating a catalytic material onto the support or carrier is as described in U.S. Pat. No. 4,077,912. These coating techniques were used to produce a catalyst for the oxidation of n-butane to maleic anhydride in U.S. Pat. No. 4,312,787.